docs: def libdmtx_function(fname, restype, *args):
      """Returns a foreign function exported by `libdmtx`.
  
      Args:
          fname (:obj:`str`): Name of the exported function as string.
          restype (:obj:): Return type - one of the `ctypes` primitive C data
          types.
          *args: Arguments - a sequence of `ctypes` primitive C data types.
  
      Returns:
          cddl.CFunctionType: A wrapper around the function.
      """
      prototype = CFUNCTYPE(restype, *args)
      return prototype((fname, load_libdmtx()))